1. Field of the Invention
The present invention relates generally to brachytherapy seeds used for radiation therapy. More particularly, the present invention relates to methods and apparatus for loading delivery systems for brachytherapy seeds used in radiation therapy.
2. Description of the Related Art
Radiation therapy is the treatment of diseases, especially the treatment of tumors, including malignant tumors, with radiation. In radiation therapy, the ultimate aim is to destroy the malignant tissue without causing excessive radiation damage to nearby healthy, and possibly vital, tissue. This is difficult to accomplish because of the proximity of malignant tissue to healthy tissue.
Medical personnel and investigators have developed methods for preferentially irradiating deep seated diseased tissue as opposed to healthy tissue. These methods include the use of high energy x-ray beams together with cross fire and rotational techniques which create a radiation pattern that is maximized at the site of the diseased tissue. Nonetheless, some absorption and damage inevitably occurs to healthy tissue in the path through which radiation passes to arrive at deep seated diseased tissue.
One method of limiting the zone of irradiation utilizes radioactive xe2x80x9cseeds,xe2x80x9d which are permanently implanted at the zone to be irradiated. Such seeds contain a radioactive isotope disposed within a capsule. The seeds are injected or implanted into body tissue at the site to be treated. The small size of therapeutic seeds allows the seeds to be inserted within tissue to be treated, in order to totally surround the tissue.
The advantage of interstitial implantation of a radiation-emitting article for localized tumor treatment have long been recognized. Interstitially implanted articles concentrate the radiation at a zone where radiation treatment is needed, i.e., near or within the tumor in order to directly affect surrounding tumor tissue, while exposing normal, healthy tissue to substantially less radiation than beaming radiation into the body from an external source.
Implanting radioactive articles directly into solid tumors to destroy the tumors is a therapy referred to as brachytherapy (i.e., short-range therapy). This form of therapy permits the application of larger doses of radiation directly to the tumor.
A seed applicator, such as shown and described in U.S. Pat. Nos. 5,860,909 and 5,242,373, the disclosures of which are hereby expressly incorporated herein by reference, can be used to accomplish correct placement of the seeds. The apparatus described in these patents are operable to implant individual seeds in spaced relationship.
Another method and approach for implanting brachytherapy seeds in or near a tumor utilizes seeds loaded within suture material, such as the RAPID STRAND(copyright) product available from Medi-Physics, Inc. Also, see Langton, et. al. U.S. Pat. No. 5,460,592, the disclosure of which is hereby incorporated herein by reference. The seeds are precisely positioned within the suture material, which may then be stiffened to retain the seeds therein and in their precise locations. An introducer is used to implant the strand of seed containing suture within the patient. The suture material retains the seeds at the desired locations until healing incorporates them into the tissue. The suture material is also bioabsorbable, and upon biodegradation of the suture material, the seeds are held in the tissue at the desired locations and with precise spacing.
The seeds utilized in either of these applications are remarkably small. The radioactive material itself, usually a portion of doped wire, is inserted and retained within a capsule. The capsule is typically a cylinder of less than 0.1550 in length and less than 0.030 in diameter. Alternatively, the capsule may have a spherical or oval shape
To facilitate handling of the seeds during implantation, the applicators described in U.S. Pat. Nos. 5,860,909 and 5,242,373 utilize a magazine that holds a number of seeds. The seeds are delivered from the magazine into the applicator, from which they are implanted within the patient. The RAPID STRAND(copyright) product itself retains the seeds and facilitates handling during implantation.
While use of applicators or the RAPID STRAND(copyright) product greatly facilitates the implantation of seeds into patients, the loading of seeds into magazines or suture material remains largely a manual task. A worker given sufficient training and learning time can become quite skilled at the tasks necessary for loading a magazine or suture with seeds. At best, however, the worker may become capable of preparing a single magazine or strand of suture in several minutes time. In addition, aside from the labor intensive nature of this process, fatigue, repetitive motion injuries and radiation exposure limit the time a skilled worker may continue in the task. Manual magazine or suture loading also requires the use of tweezers, necessary for handling the small seeds, which may also result in damage to the seeds, and process variation remains worker dependant and difficult to control.
The present invention provides apparatus and methods for loading delivery systems, such as seed magazines and suture material, with seeds which greatly increases productivity, reduces process variation and reduces the risk of handling damage to the seeds. Importantly, the apparatus and methods of the present invention reduce potential risks to workers.
In a first aspect of the invention there is provided an automated method of loading a delivery system for brachytherapy seeds which comprises the steps of:
a) securing the delivery system to be loaded;
b) communicating seeds from a supply of seeds into the delivery system; and
c) repeating step b) to load a plurality of seeds.
In a second aspect of the invention there is provided an apparatus for loading a delivery system for brachytherapy seeds comprising:
a) means for retaining a delivery system to be loaded with seeds; and
b) means for communicating individual seeds from a supply of seeds to said delivery system.
In one embodiment of either the first or second aspect of the present invention, a magazine to be loaded with seeds is positioned within a loading fixture. A vibratory feeder communicates seeds to a staging area adjacent the fixtured magazine, and a pusher member cycles to load seeds from the staging area into the magazine.
In another embodiment of either the first or second aspect of the present invention, suture material is loaded onto a cannula, which is then precisely positioned within the loading apparatus. A magazine containing a plurality of seeds is loaded to the loading apparatus. Seeds are introduced from the magazine into the cannula, and a pusher communicates the seeds along the cannula and proximate to an end thereof. A gripper, positioned adjacent the end of the cannula retracts the suture material drawing the seed from the cannula along with a precise length of suture material. The loader apparatus is operated until a desired number of seeds are loaded within the suture material, which is then removed from the loader and arranged for subsequent finish processing.
Definitions:
The following are definitions of various terms used in the foregoing specification.
Brachytherapy seed: A brachytherapy seed comprises: (1) a radioactive source, comprising (a) a radioisotope, disposed on (b) a carrier, and (2) a casing containing the radioactive source. In some embodiments, the carrier also serves as the casing.
The seed is of an overall size and dimensions suitable for its intended use. Seeds for use in the treatment of prostate cancer are, for example, typically substantially cylindrical in shape, about 4.5 mm long with a diameter of 0.8 mm. For use in the treatment of restenosis, a seed is of suitable dimensions to be inserted inside a coronary artery, for example, a length of about 10 mm and a diameter of about 1 mm, preferably a length of about 5 mm and a diameter of about 0.8 mm, and most preferably a length of about 3 mm and a diameter of about 0.6 mm. A seed also can be oval or substantially spherical in shape.
Radioisotope: The radioactive isotope disposed on the surface of the carrier is not limited and is selected based on the type and strength of the radiation that is desired, the half-life of the radioisotope, and the disease or condition to be treated. Non-limiting examples of useful radioisotopes include iodine-125, palladium-103, cesium-131, gold-198, thulium-170, chromium-56, arsenic-73, yttrium-90, and mixtures thereof. In addition, radioactive isotopes of samarium, tantalum, radon, radium, cobalt, iridium, and mixtures thereof, also can be used in brachytherapy seeds. Other gamma ray emitting elements and radioactive isotopes, including mixtures of one or more radiation sources capable of emitting therapeutically useful forms of radiation (e.g., gamma rays, alpha particles, beta particles, Auger electrons, X-rays, and electromagnetic waves) also are useful, provided they are presented in a form and in amounts which are useful in radiation therapy. Several other examples of useful radioisotopes are disclosed in Good, U.S. Pat. No. 5,342,283, the disclosure of which is hereby expressly incorporated herein by reference. The radioactive isotope is applied to the carrier by techniques that are well known in the art. Particularly preferred radioisotopes included palladium-103 and iodine-125.
Carrier: Suitable carriers for the radioisotopes include, but are not limited to, support materials, such as plastics, graphite, zeolites, ceramics, glasses, metals, polymer matrices, ion-exchange resins, and other, preferably porous, materials. The support material can be in the form of a bead, wire, or rod. The support materials can be encapsulated in a hollow sealed casing, for example a metal container, or the support material can be coated with an electroplated shell, for example a layer of a metal, such as silver or nickel. Alternatively, the carrier can be a hollow sealed container directly encapsulating the radioisotope, without, for example, the need for a biocompatible support material.
The carrier incorporating the radioisotope also can be a polymer matrix, or a plastic or ceramic composite, and/or may form part of a container wall. For example, if a metal alloy is used to form a container, then a component of the alloy can be a suitable radioisotope. If a container is made from a composite material, a component of the composite may be a suitable radioisotope.
Specific, non-limiting, examples of carriers are silver and copper because these metals provide good X-ray visualization and because commonly used radioactive isotopes, such as iodine and palladium, can be easily attached to a silver or copper surface by chemical or electroplating processes. Other X-ray opaque metals, such as gold and iron, for example, can be used as a carrier for purposes of the invention. Likewise, a suitable metal can be deposited (chemically or by using xe2x80x9csputteringxe2x80x9d and xe2x80x9cion platingxe2x80x9d techniques) onto a substrate other than a metal, e.g., a polypropylene filament, preferably such that the thickness of the metallic coating on the substrate exceeds about 0.050 mm to ensure X-ray visualization.
Casing: Suitable casing materials include biocompatible metals or metal alloys such as titanium, gold, platinum and stainless steel: plastics such as polyesters and vinyl polymers of polyurethane, polyethylene and poly(vinyl acetate); composites of graphite, and glass such as matrices comprising silicon oxide. The container also can be plated on the outside with a biocompatible metal, for example, gold or platinum.
Preferred suitable casing materials are biocompatible metals, and typically low atomic numbered metals, such as stainless steel alloy or titanium. Higher atomic number metals, such as gold and platinum, attenuate too much radiation emanating from the radioisotope-laden carrier to be useful per se. However, higher atomic numbered biocompatible metals are useful as a plating over various low atomic number materials such as beryllium, which otherwise is too toxic if used without an outer coating. Other suitable casing materials include, but are not limited to, tantalum, nickel alloys, copper alloys, and aluminum alloys.
Titanium, which has a low atomic number and a high strength-to-weight ratio, is the most preferred casing material. Titanium is exceptionally corrosion-resistant, and is satisfactory from the standpoint of tissue compatibility and non-toxicity. Preferably, the titanium is a pure alloy to assure good working properties.
The casing can have at least part of one surface of which is roughened, shaped, or otherwise treated whereby ultrasound visibility of the seed is enhanced.
Suture Material: The suture material is a bioabsorbable material made of any natural or synthetic material that is absorbable in a living body. Non-limiting examples of natural absorbable materials, as disclosed in U.S. Pat. No. 4,697,575, are the polyester amides from glycolic or lactic acid, such as the polymers and copolymers of glycolate and lactate, polydioxanone and the like. Such polymeric materials are more fully described in U.S. Pat. Nos. 3,565,869; 3,636,956; 4,052,988 and European Patent Application 30822. Specific and non-limiting examples of absorbable polymeric materials that can be used as suture materials are polymers marketed by Ethicon, Inc., Somerville, N.J. under the trademarks xe2x80x9cVICRYLxe2x80x9d and xe2x80x9cPDS.xe2x80x9d
The suture material preferably maintains its integrity for from 1 to about 14 days. Preferably, the suture material is absorbed in living tissue in a period of time from about 70-120 days.